Long stroke hammer



May 2,1933. E. w. STEVENS LONG STROKE HAMMER Filed Feb.

INVENTOR. fakvcrra I44 5zeVe/7s ATTORNEY.

Patented May 2, 1933 UNITED STATES PATENT OFFICE EDWARD W. STEVENS, OF DETROIT, MICHIGAN, AS SIGNOR T CHICAGO PNEUMATIC.

TOOL COMPANY, OF NEW YORK, N. Y., A CORPORATION OF NEW JERSEY LONG srnoxn HAMMER This invention relates to fluid pressure percussive tools having a long stroking piston adapted to deliver heavy, rapid blows as in riveting. More particularly it relates to tools having a piston-controlled main exhaust and an automatically thrown valve for distributing the motive fluid to the opposite ends of the piston chamber. Such tools have a relativelyshort stroke and in 0 order to secure a longer stroke some means are required for delaying or relieving the pressure built up at the opposite ends of the piston chamber by the piston after it has overrun the main exhaust. In certain aspects the present invention may be considered an improvement upon 01' further development of the invention disclosed and claimed in my copending applications, Serial No. 131,680, filed February 27, 1930 and Serial No. 508,126, filed January 12, 1931.

One object of the invention is to provide a simple, inexpensive and positively acting venting arrangement to effect long stroking in tools of the described type. Another object is to utilize live pressurefluid which has passed the automatic distributing valve foroperating auxiliary exhaust or relief valves. Another object is to produce a form or type of relief valve arrangement whichutilizes simple and well known standard commercial articles and which will effect a seal without substantial loss of motive fluid. Other objects will be apparent from the detailed description which follows.

The invention involves the use of special relief means which may comprise two exhaust or relief Valves, one for the relief of each end of the piston chamber. Means are provided positively to actuate both exhaust valves simultaneously and in unison, the one to open a relief port and the other to seal a relief port. The exhaust valves are individually acted upon in alternation by pressure fiuid released by the distributing valve and the movement of one exhaust valve is communicated directly to the other. The preferred connection is by a movable member such as a pin which loosely engages both valves and is of such length that when Serial No. 515,212.

one exhaust valve is seated, the intervening member or pin acts asa spacer to hold the other exhaust valve 0E its seat. By preference simple ball valves are used for the auxiliary exhaust or relief valves.

In order to illustrate theinventiomone concrete embodiment thereof is shown in the accompanying drawing, in which:

Fig. 1 is a longitudinal sectional view;

Fig. 2 is a view similar to Fig. 1 showing the control valves in different positions and a pcprtion of the throttle handle in elevation; an

Fig. 3 is a transverse sectional view substantially on the line 33 of Fig. 1.

The embodiment of the invention chosen for the purpose of illustation comprises a pneumatic hand hammer having a cylinder 4 providing a piston chamber within which reciprocates a hammer piston 5 for imparting impact blows to the shank of a work ing tool of any suitable type such as a rivet set 6 extending into the front end of cylinder-4. The cylinder has one or more main atmospheric exhaust ports 7 extending through the wall thereof under control of piston 5. The reciprocations of the piston are controlled by a distributing r valve 8 which distributes motive fluid in alternation tending to the front end thereof. Both pasv sages extend rearwardly into chambers 11 and 12 respectively provided in a lid member13 closing the rear end of the piston chamber and interposed between cylinder 1 and the inner wall of a handle sleeve 14 which may have integral therewith a grip portion 14a. The handle may provide a conduit 14?) for motive fluid controlled by a throttle valve (not shown) arranged to be actuated by the conventional thumb lever 1 10 (Fig. 2). Lid 13 provides vent ports 11a and 12a for chambers 11 and 12 which ports are diametrically opposed to each other and in alignment These ports'provide seats for valves 15 and 16 which are preferably of the ball type. A push rod 17 is slidably mounted in a bore in lid 13 for loose engagement with valves 15 and 16 and is projectable through ports 11a and 12a to cause valves 15 and 16 to move simultaneously and in unison as will presently be described. Passages 11b and 12b extend from vent ports 11a and 12a to a vent chamber 18 in the rear wall of handle sleeve 14 whence extend a. series of ports 18a to atmosphere. A retainer sleeve 19 is forced over the reduced rear end of lid 13 to close chambers Hand 12 and to retain valves 15 and 16 and push rod 17in place.

By preference cylinder 4 is reduced at its rearward end to provide a slightly elliptical extension with opposed arcuate valve seats 4a and 4?) having ports at and 10a opening into passages 9 and 10 respectively. Also by preference distributing valve 8 is in the form of a narrow ring sleeved over the ellipticalprojection on cylinder 4. and of less length than the latter so that pressure fluid admitted by conduit 14?) to chamber 20 surrounding valve 8 may pass over the edges of the same at either of the valve seats not engaged by the valve, as at seat 1a in Fig. 1 and seat 41) in Fig. 2. This ring valve arrangement conforms to that shown in Figs. 1 to 3 of my aforesaid copending application, Serial No. 508,126, and its manner of operation is the same. Handle sleeve 14 may be'secured to cylinder 4 beyond the valves in any suitable manner as by a threaded connection at 21.

The'cycle of operation is as follows: In Fig. 1 live air'entering by passage 14?) fills the annular chamber 20 around distributing valve 8 and passes over the edges or ends of the valve and beneath the same at seat 4a through port 960 and into passage 9. Since passage 9 connects both with auxiliary valve chamber 11 and the rear end of the piston chamber, the live fluid acts to force ball valve 15 upwardly against its seat to close port 11a and through push rod 17 forces ball valve 16 off port 12a. At the same time the rear end of the piston chamber is filled with motive fluid which drives piston 5 on its forward or working stroke. Air in advance of the piston escapes through main exhaust port 7 until the latter is closed by the piston and thereafter continues to escape through passage 10, chamber 12, port 12a, passage 1%, vent chamber 18 and atmospheric port-s 18a. As piston 5 passes beyond and uncovers main exhaust 7 there is a quick drop in pressure in the rear end of the piston chamber which extends back to passage 9 and to the inner face of ring valve 8. Valve 8 moves upwardly into engagement with seat 4a and thereby uncovers seat 46, the movement beingdue to the body of live air surrounding the valve which creates a force and due to the natural tendency. ofthe valve to follow the flow of air. It is to be understood that the area of the passages leading from the inner face of the valve exceeds the inlet space between the valve face and the seat in order to make it possible for the valve to shift when the exhaust port 7 is uncovered and the air in the piston chamber is released to atmosphere.

When the valve shifts, as indicated, it uncovers port 10a and passage 10 is filled with pressure fluid. This acts on valve 16 forcing it downwardly to close vent port 120 and acting through push rod 17 to unseat valve 15. At the same time the pressure fluid catches piston 5 as it rebounds from "striking rivets set 6 and drives it rearward ly on its non-working stroke. After piston 5 has closed main exhaust port 7, the air in advance'of it escapes through passage 9, chamber 11, port 11a, passage 11?), chamber 18 and atmospheric ports 18a. When piston 5 passes beyond main exhaust 7 the pressure falls in the forward end of the piston chamher and in passage 10 and at Valve seat 412 so that valve 8 again returns to the position shown in Fig. 1 and the pressure fluid then admitted to passage 9 causes auxiliary valves 15 and 16 to move in unison to their upper position thus completing the cycle.

It is to be noted that main exhaust port 7 is not placed centrally of the piston chamber but toward the front of thesame in order that a forceful blow may be delivered by piston 5 upon the working-tool 6. On its rearward movement piston 5 must be stopped and reversed by pressure fluid admitted through passage 9 and considerablemovement of piston 5 beyond main exhaust port 7 is secured in this direction due to the fact that the rear end of the piston chamber is vented through the auxiliary valve arrangementuntil the valves are shifted and due tothe factthat the shifting of the valves is delayed beyond the time required on the forward stroke of the piston'by the momentum acquired by the piston and by the greater length of passage '10 as .compared with passage 9.

While the invention has been herein disclosed in what is now considered to be its preferred form, it is to be understood that the invention is not limited to the specific details thereof, but covers all changes, modifications and adaptations within the scope of the appended claims.

I claim as my invention:

1. A fluid pressure percussive tool com-v prising acylinder providing a piston chamber and having an exhaust port to atmosphere, a hammer piston reciprocable in said cylinder and controlling said port, said cylinder having passages extending to the opposite ends of said pistonchamber, an automatically thrown valve mounted directly upon said-cylinder for controlling the dis tribution of motive fluid in alternation to said passages, a head member telescoped over .t-he rear. end of said cylinder and enclosing said valve, and means within said member for venting said passages in reverse alternation to the admission of motive fluid thereto by said va ve, said valve-and venting means respectively being disposed in adjacent transverse planes for movement transversely to the axis of the tool.

2. A fluid pressui'e percussive tool comprising a cylinder providing a piston chamber and having an exhaust port to atmosphere, a hammer piston reciprocable in said cylinder and controlling said port, said cylinder having passages extending to the opposite ends or said piston chamber, an automatically thrown valve mounted directly upon said cylinder for controlling the distribution of motive fluid in alternation to said passages, a head member telescoped over the rear end of said cylinder and en closing said valve, and means within said member for venting said passages in reverse alternation to the admission of motive fluid thereto by said valve and controlled by the motive fluid so admitted.

3. A fluid pressure percussive tool comprising a cylinder providing a piston chamber and having an exhaust port to atmos phere, a hammer piston reciprocable in said cylinder and controlling said port, said cylinder having passages extending to the opposite ends of said piston chamber, an automatically thrown valve mounted directly upon said cylinder for controlling the distribution of motive fluid in alternation to said passages, a head member telescoped over therear end of said cylinder and enclosing said valve, a lid within said head member and in abutting engagement with said cylinder, said lid providing vents con nected with said passages, and valve means controlling said vents in reverse alternation to the admission of motive fluid to said passages by said valve. r

4. A fluid pressure percussive tool comprising a cylinder providing a piston chamher and having an exhaust port to atmosphere, a hammer piston reciprocable in said cylinder and controlling said port, said cylinder having passages extending to the opposite ends of said piston chamber, an automatically thrown valve mounted directly upon said cylinder for controlling the distribution of motive fluid in alternation to said passages, a head member telescoped over the rear end of said cylinder and enclosing said valve, a lid within said head and in abutting relation with said cylinder, said lid providing vents connected to said passages, and valves for controlling said vents moving in unison with each other but in sequence to said distributing valve to vent said passages in alternation with the admission of pressure fluid thereto by said distributing valve.

5. A fluid pressure percussive tool comprising a cylinder providing a piston chamber and having an exhaust port to atmosphere, a hammer piston reciprocable in said cylinder and controlling said port, said cylinder having passages extending to the opposite ends of said chamber, a ring valve telescoped over the rear end of said cylinder for movement transversely thereof automatically to control the distribution of mo tive fluid in alternation to said passages, a closure member sleeved over said cylinder and enclosing said valve, a lid within said closure member in abutting relation with said cylinder, said lid providing vents connected to said passages, separate individual valves for controlling said vents, and a spacmg member interposed between said vent valves to effect their movement in unison with each other.

Signed by me at Detroit in the County of Wayne and State of Michigan this 9 day of February, 1931.

ED'WARD W. STEVENS. 

